//========================================================================
// GLFW 3.3 Linux - www.glfw.org
//------------------------------------------------------------------------
// Copyright (c) 2002-2006 Marcus Geelnard
// Copyright (c) 2006-2017 Camilla Löwy <elmindreda@glfw.org>
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would
//    be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
//    be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
//    distribution.
//
//========================================================================
// It is fine to use C99 in this file because it will not be built with VS
//========================================================================

#include "internal.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/inotify.h>
#include <fcntl.h>
#include <errno.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifndef SYN_DROPPED // < v2.6.39 kernel headers
// Workaround for CentOS-6, which is supported till 2020-11-30, but still on v2.6.32
#define SYN_DROPPED 3
#endif

// Apply an EV_KEY event to the specified joystick
//
static void handleKeyEvent(_GLFWjoystick* js, int code, int value) {
  _glfwInputJoystickButton(js,
                           js->linjs.keyMap[code - BTN_MISC],
                           value ? GLFW_PRESS : GLFW_RELEASE);
}

// Apply an EV_ABS event to the specified joystick
//
static void handleAbsEvent(_GLFWjoystick* js, int code, int value) {
  const int index = js->linjs.absMap[code];

  if (code >= ABS_HAT0X && code <= ABS_HAT3Y) {
    static const char stateMap[3][3] =
        {
            {GLFW_HAT_CENTERED, GLFW_HAT_UP, GLFW_HAT_DOWN},
            {GLFW_HAT_LEFT, GLFW_HAT_LEFT_UP, GLFW_HAT_LEFT_DOWN},
            {GLFW_HAT_RIGHT, GLFW_HAT_RIGHT_UP, GLFW_HAT_RIGHT_DOWN},
        };

    const int hat = (code - ABS_HAT0X) / 2;
    const int axis = (code - ABS_HAT0X) % 2;
    int* state = js->linjs.hats[hat];

    // NOTE: Looking at several input drivers, it seems all hat events use
    //       -1 for left / up, 0 for centered and 1 for right / down
    if (value == 0)
      state[axis] = 0;
    else if (value < 0)
      state[axis] = 1;
    else if (value > 0)
      state[axis] = 2;

    _glfwInputJoystickHat(js, index, stateMap[state[0]][state[1]]);
  } else {
    const struct input_absinfo* info = &js->linjs.absInfo[code];
    float normalized = value;

    const int range = info->maximum - info->minimum;
    if (range) {
      // Normalize to 0.0 -> 1.0
      normalized = (normalized - info->minimum) / range;
      // Normalize to -1.0 -> 1.0
      normalized = normalized * 2.0f - 1.0f;
    }

    _glfwInputJoystickAxis(js, index, normalized);
  }
}

// Poll state of absolute axes
//
static void pollAbsState(_GLFWjoystick* js) {
  for (int code = 0; code < ABS_CNT; code++) {
    if (js->linjs.absMap[code] < 0)
      continue;

    struct input_absinfo* info = &js->linjs.absInfo[code];

    if (ioctl(js->linjs.fd, EVIOCGABS(code), info) < 0)
      continue;

    handleAbsEvent(js, code, info->value);
  }
}

#define isBitSet(bit, arr) (arr[(bit) / 8] & (1 << ((bit) % 8)))

// Attempt to open the specified joystick device
//
static GLFWbool openJoystickDevice(const char* path) {
  for (int jid = 0; jid <= GLFW_JOYSTICK_LAST; jid++) {
    if (!_glfw.joysticks[jid].present)
      continue;
    if (strcmp(_glfw.joysticks[jid].linjs.path, path) == 0)
      return GLFW_FALSE;
  }

  _GLFWjoystickLinux linjs = {0};
  linjs.fd = open(path, O_RDONLY | O_NONBLOCK);
  if (linjs.fd == -1)
    return GLFW_FALSE;

  char evBits[(EV_CNT + 7) / 8] = {0};
  char keyBits[(KEY_CNT + 7) / 8] = {0};
  char absBits[(ABS_CNT + 7) / 8] = {0};
  struct input_id id;

  if (ioctl(linjs.fd, EVIOCGBIT(0, sizeof(evBits)), evBits) < 0 ||
      ioctl(linjs.fd, EVIOCGBIT(EV_KEY, sizeof(keyBits)), keyBits) < 0 ||
      ioctl(linjs.fd, EVIOCGBIT(EV_ABS, sizeof(absBits)), absBits) < 0 ||
      ioctl(linjs.fd, EVIOCGID, &id) < 0) {
    _glfwInputError(GLFW_PLATFORM_ERROR,
                    "Linux: Failed to query input device: %s",
                    strerror(errno));
    close(linjs.fd);
    return GLFW_FALSE;
  }

  // Ensure this device supports the events expected of a joystick
  if (!isBitSet(EV_KEY, evBits) || !isBitSet(EV_ABS, evBits)) {
    close(linjs.fd);
    return GLFW_FALSE;
  }

  char name[256] = "";

  if (ioctl(linjs.fd, EVIOCGNAME(sizeof(name)), name) < 0)
    strncpy(name, "Unknown", sizeof(name));

  char guid[33] = "";

  // Generate a joystick GUID that matches the SDL 2.0.5+ one
  if (id.vendor && id.product && id.version) {
    sprintf(guid, "%02x%02x0000%02x%02x0000%02x%02x0000%02x%02x0000", id.bustype & 0xff, id.bustype >> 8, id.vendor & 0xff, id.vendor >> 8, id.product & 0xff, id.product >> 8, id.version & 0xff, id.version >> 8);
  } else {
    sprintf(guid, "%02x%02x0000%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x00", id.bustype & 0xff, id.bustype >> 8, name[0], name[1], name[2], name[3], name[4], name[5], name[6], name[7], name[8], name[9], name[10]);
  }

  int axisCount = 0, buttonCount = 0, hatCount = 0;

  for (int code = BTN_MISC; code < KEY_CNT; code++) {
    if (!isBitSet(code, keyBits))
      continue;

    linjs.keyMap[code - BTN_MISC] = buttonCount;
    buttonCount++;
  }

  for (int code = 0; code < ABS_CNT; code++) {
    linjs.absMap[code] = -1;
    if (!isBitSet(code, absBits))
      continue;

    if (code >= ABS_HAT0X && code <= ABS_HAT3Y) {
      linjs.absMap[code] = hatCount;
      hatCount++;
      // Skip the Y axis
      code++;
    } else {
      if (ioctl(linjs.fd, EVIOCGABS(code), &linjs.absInfo[code]) < 0)
        continue;

      linjs.absMap[code] = axisCount;
      axisCount++;
    }
  }

  _GLFWjoystick* js =
      _glfwAllocJoystick(name, guid, axisCount, buttonCount, hatCount);
  if (!js) {
    close(linjs.fd);
    return GLFW_FALSE;
  }

  strncpy(linjs.path, path, sizeof(linjs.path) - 1);
  memcpy(&js->linjs, &linjs, sizeof(linjs));

  pollAbsState(js);

  _glfwInputJoystick(js, GLFW_CONNECTED);
  return GLFW_TRUE;
}

#undef isBitSet

// Frees all resources associated with the specified joystick
//
static void closeJoystick(_GLFWjoystick* js) {
  close(js->linjs.fd);
  _glfwFreeJoystick(js);
  _glfwInputJoystick(js, GLFW_DISCONNECTED);
}

// Lexically compare joysticks by name; used by qsort
//
static int compareJoysticks(const void* fp, const void* sp) {
  const _GLFWjoystick* fj = fp;
  const _GLFWjoystick* sj = sp;
  return strcmp(fj->linjs.path, sj->linjs.path);
}

//////////////////////////////////////////////////////////////////////////
//////                       GLFW internal API                      //////
//////////////////////////////////////////////////////////////////////////

// Initialize joystick interface
//
GLFWbool _glfwInitJoysticksLinux(void) {
  const char* dirname = "/dev/input";

  _glfw.linjs.inotify = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
  if (_glfw.linjs.inotify > 0) {
    // HACK: Register for IN_ATTRIB to get notified when udev is done
    //       This works well in practice but the true way is libudev

    _glfw.linjs.watch = inotify_add_watch(_glfw.linjs.inotify,
                                          dirname,
                                          IN_CREATE | IN_ATTRIB | IN_DELETE);
  }

  // Continue without device connection notifications if inotify fails

  if (regcomp(&_glfw.linjs.regex, "^event[0-9]\\+$", 0) != 0) {
    _glfwInputError(GLFW_PLATFORM_ERROR, "Linux: Failed to compile regex");
    return GLFW_FALSE;
  }

  int count = 0;

  DIR* dir = opendir(dirname);
  if (dir) {
    struct dirent* entry;

    while ((entry = readdir(dir))) {
      regmatch_t match;

      if (regexec(&_glfw.linjs.regex, entry->d_name, 1, &match, 0) != 0)
        continue;

      char path[PATH_MAX];

      snprintf(path, sizeof(path), "%s/%s", dirname, entry->d_name);

      if (openJoystickDevice(path))
        count++;
    }

    closedir(dir);
  }

  // Continue with no joysticks if enumeration fails

  qsort(_glfw.joysticks, count, sizeof(_GLFWjoystick), compareJoysticks);
  return GLFW_TRUE;
}

// Close all opened joystick handles
//
void _glfwTerminateJoysticksLinux(void) {
  int jid;

  for (jid = 0; jid <= GLFW_JOYSTICK_LAST; jid++) {
    _GLFWjoystick* js = _glfw.joysticks + jid;
    if (js->present)
      closeJoystick(js);
  }

  regfree(&_glfw.linjs.regex);

  if (_glfw.linjs.inotify > 0) {
    if (_glfw.linjs.watch > 0)
      inotify_rm_watch(_glfw.linjs.inotify, _glfw.linjs.watch);

    close(_glfw.linjs.inotify);
  }
}

void _glfwDetectJoystickConnectionLinux(void) {
  if (_glfw.linjs.inotify <= 0)
    return;

  ssize_t offset = 0;
  char buffer[16384];
  const ssize_t size = read(_glfw.linjs.inotify, buffer, sizeof(buffer));

  while (size > offset) {
    regmatch_t match;
    const struct inotify_event* e = (struct inotify_event*)(buffer + offset);

    offset += sizeof(struct inotify_event) + e->len;

    if (regexec(&_glfw.linjs.regex, e->name, 1, &match, 0) != 0)
      continue;

    char path[PATH_MAX];
    snprintf(path, sizeof(path), "/dev/input/%s", e->name);

    if (e->mask & (IN_CREATE | IN_ATTRIB))
      openJoystickDevice(path);
    else if (e->mask & IN_DELETE) {
      for (int jid = 0; jid <= GLFW_JOYSTICK_LAST; jid++) {
        if (strcmp(_glfw.joysticks[jid].linjs.path, path) == 0) {
          closeJoystick(_glfw.joysticks + jid);
          break;
        }
      }
    }
  }
}

//////////////////////////////////////////////////////////////////////////
//////                       GLFW platform API                      //////
//////////////////////////////////////////////////////////////////////////

int _glfwPlatformPollJoystick(_GLFWjoystick* js, int mode) {
  // Read all queued events (non-blocking)
  for (;;) {
    struct input_event e;

    errno = 0;
    if (read(js->linjs.fd, &e, sizeof(e)) < 0) {
      // Reset the joystick slot if the device was disconnected
      if (errno == ENODEV)
        closeJoystick(js);

      break;
    }

    if (e.type == EV_SYN) {
      if (e.code == SYN_DROPPED)
        _glfw.linjs.dropped = GLFW_TRUE;
      else if (e.code == SYN_REPORT) {
        _glfw.linjs.dropped = GLFW_FALSE;
        pollAbsState(js);
      }
    }

    if (_glfw.linjs.dropped)
      continue;

    if (e.type == EV_KEY)
      handleKeyEvent(js, e.code, e.value);
    else if (e.type == EV_ABS)
      handleAbsEvent(js, e.code, e.value);
  }

  return js->present;
}

void _glfwPlatformUpdateGamepadGUID(char* guid) {
}
